This invention relates to a fixture for explosively welding a tube into a tubesheet and, more particularly, to such a fixture for providing sequential detonation of a plurality of explosives.
In order to secure a plurality of heat exchange tubes in corresponding bores formed in a tubesheet, several techniques have evolved. One of the most effective techniques is to explosively force each tube against the internal wall defining the corresponding bore in the tubesheet, which involves detonating an explosive placed within the tube so that the resulting explosive forces acting on the tube expands it and forces the outer surface of the tube to the bore wall causing a weld.
In conventional welding methods of this nature, several problems exist. For example, the materials used to fabricate the tubes and/or the tubesheets are often incompatible with these types of techniques. Therefore in order to permit the welding, materials have to be used which, although weldable, are more susceptible to high temperature corrosion.
Also, according to some of these techniques, only one tube can be formed at a time, which is unacceptable in hazardous locations where operator residence time is limited.
Further, due to the large number of different tube sizes, tubesheet designs and material combinations, a corresponding variance in the sizes of the explosive insert, are required which makes the cost of fabricating injection dies and tooling for the inserts impractical from a cost standpoint.